Mr, Porstmr's Observations on Ratcheugh Crag. 77 



PL X. Fig. 1), is taken, not in the face of the CHff, but in the dip and 

 rise direction, at the angle formed by the breach — at a ("see the rough 

 sketchj. I selected this point with a view of displaying more clearly 

 the position of the Basaltic columns, and the overlying bed of Lime- 

 stone. On examining the section, it will be observed that the columns of 

 Basalt, instead of being perpendicular to the horizon, stand at a right 

 angle with the plane of the inclination of the strata, and that the same 

 appearance is exhibited by the "backs," or partings , cutting through the 

 bed of Limestone above it. May it not be inferred from this, that the 

 present inclined position both of the Basalt and Limestone has been as- 

 sumed after their deposition and consolidation ? The bed of Limestone 

 forming the top of the Cliff is divided into nine different layers, none of 

 which appear to have been affected by the vicinity of the Basalt, except 

 the lowest. This layer is 10 inches thick ; divided from the layer above 

 it by a Shale bed of 3 inches ; but, having its lower facing in immediate 

 contact with the top of the Basaltic columns. For 4 or 5 inches above the 

 junction the colour of the Limestone is changed from dark-grey to 

 brown, and its texture is more compact and crystalline ; this appear- 

 ance gradually fades in passing upwards, and, at a distance of 6 or 7 

 inches from the junction, the Limestone assumes its usual characters. 

 In point of position, inclination, &c. the Limestone and Basalt are per- 

 fectly conformable to each other, dipping at an angle of 14<° in the di- 

 rection of S. 69° E. 



On comparing the above-described section with that at Snableases 

 Quarry fsee PI. X. Fig. 2), a remarkable change in the relative position of 

 the strata will be obsei'vedj here, the Limestone, instead of reposing upon 

 60 or 80 feet of columnar Basalt, is underlaid by 2 feet of that rock, in 

 a compact mass, and overlaid, first, by a stratum of Shale, changed in 

 its appearance so as to resemble porcelain Jasper, and then by a colum- 

 nar Basaltic bed of 43 feet in thickness. In external appearance the 

 Limestone appears little, if at all, altered by the vicinity of the Basalt, 

 although the lower, or 2-feet, bed of the latter is in actual contact with 

 it. This 2-feet bed is considered as usurping the place of the thin seam 

 of Coal (which at Dunsheugh Pit, and elsewhere, is found to underlie 



